FI73326B - FOERFARANDE OCH ANORDNING FOER UPPTAGNING OCH AOTERGIVNING AV BILDINFORMATION VID ROENTGENPANORAMAAVBILDNING. - Google Patents

Description

1 73326

A method and apparatus for recording and reproducing image information in X-ray panoramic imaging. - Refinement and ordering of data and information from X-ray data.

The invention relates to a method and apparatus for recording and reproducing image information in X-ray panoramic imaging, in which an X-ray beam passing through a subject is swept over an imaging area and information representing the desired layer of the subject is extracted from the total information of the beam passing through the subject.

Such a panoramic image is used, for example, in the description of a dental arch. One example of such a device is disclosed in U.S. Patent No. 4,263,513 and another example in U.S. Patent No. 4,589,122.

Before presenting the solution according to the invention, the essential theory of panoramic imaging will be described below with reference to the accompanying Figures 1-4.

Assume that the object to be photographed rotates around point 0 at the time of consideration. For example, a narrow beam from the focus F of the X-ray tube projects its target point K on the center line to the point P at the plane under consideration, in the image plane T.

If the target point K moves downward in the image at a speed v ^, the projection point P also moves downward, but due to the greater distance from the projection center F at a higher speed

v. Examining the figure, it can be seen that P

v 1 P = P

Vk Xk This still gives 7 3 3 2 6 2 p V = = - V.

p ik k

If a film is placed on the image plane T and given a speed VF = V

a sharp image is obtained from the target point K for the film.

Dots farther from the center of rotation 0 move faster than the film and are fogged. The closer points, on the other hand, move slower than the film and are fogged as well. Acceptably sharp points determine the so-called the descriptive layer shown in Figure 1.

By placing the object, as in the case of Figure 2, the chin, on the imaging layer, a sharp image is obtained.

In addition to the above, it is known that if the film cassette is given a higher speed in one way or another than the recent ones, the imaging layer moves away from the focus F, as has happened in Fig. 3. The lower speed, on the other hand, moves the imaging layer closer to focus F. This is shown in Figure 4.

The possibility of changing the cassette speed can be e.g. used for precise placement of the imaging layer without moving the patient. This is also the case with some devices.

If, for one reason or another, the subject does not hit the imaging layer, a new imaging must be performed by moving the imaging layer in the patient. In addition to many inconveniences, this results in an increase in the required radiation dose.

The object of the invention is to provide a method and an apparatus for recording and reproducing image information in a panoramic image, so that the stored image information can be

II

3 73326 New images of the desired layers can be obtained without having to re-image the actual subject.

This object is achieved by the method according to the invention in that the total information of the beam passing through the object is stored on a memory disk and the memory disk is used to produce or display layer-by-layer images of the desired layers. During shooting, the memory disc is held still relative to the subject.

The production of layer-by-layer images from a memory disk can be performed in many different ways, some examples of which are described below. One way is to use a principle similar to conventional pan-ray layer imaging, but the subject is now a memory disk containing the same total animation as the radiation that passed through the subject. If film is used as the memory disc, images corresponding to the desired layer can be extracted from the film with visible light. The light transmitted by the film contains the same total information as the beam transmitted by the subject, so by selecting the relative speed of the light beam erasing the film and the film used for re-shooting as desired, the desired layer can be re-imaged.

When using the method and device according to the invention, the reproduction of the image does not have to be arranged in connection with the imaging device itself, but a separate, image reproducing device can be used, in which a memory disk with overall image information is inserted. In the image reproducing apparatus, an image corresponding to a certain layer is extracted from the total information of the memory disk on the film or on the screen by causing a speed difference between the operation of the memory disk and the printing or display of the image. The reproduction of the film on the film can be performed by exposing the layer image printing film through the memory plate with a narrow beam of light that sweeps the memory plate and the printing film while causing the printing film and the memory plate to have a scanning speed difference. Instead, if the image is played back on the screen, the memory disc is recorded on the camcorder, and the screen sweep speed is adjusted by adjusting the width of the image to extract the desired layer from the memory card. Briefly, in both cases, the width of the reproduced image is slightly narrower than the width of the total information image on the memory disk, whereby the width difference corresponds to the above-mentioned speed difference between the memory disk pick-up and the layer image print or screen scan.

In a screen application, the object can be viewed at different depths as if layer by layer. Thus, the desired layer or layers can be found for re-imaging. Thus, it is practical to combine the image reproduction on the film and the on-screen display so that the layer search is performed on the screen, followed by the description of the desired layer on the film.

In the following, the invention is illustrated with reference to the exemplary embodiments of Figures 5-7.

Figure 5 is a schematic top view of an embodiment of the invention. Fig. 6 schematically shows an image reproducing apparatus which is separate from the imaging device. Figure 7 schematically shows another imaging device, which is also separate from the imaging device.

In Fig. 5, the points F, O, K and P correspond to the points marked with the same letters in Fig. 1. The X-ray source 1 and the film-carrying cassette 2 are located at opposite ends of the arm 3. The arm 3 can be rotated about the axis 0 by any drive device 4. The object is a toothed arc 5. The pivot axis O can be movable relative to the object 5 and / or the arm 3 can be movable relative to the axis O and / or the cassette 2 can be movable relative to the arm 3 and still the film 2 'may be movable relative to the cassette 2. The implementation of the invention is in no way dependent on the previously known movement arrangements of these known device parts. By means of these known parts, the imaging takes place in such a way that the information part describing the desired layer is "extracted" from the total information coming to the film 2 'through the imaging beam 5 at the appropriate speed of the cassette 2'.

The invention is based on the realization that in addition to or instead of said sub-information, said total radiation information is stored, and the recording can later be used to extract the sub-information for retransmission. For this purpose, in the case of Fig. 5, there is a subject 5 and a film cassette. 2, the shape of which corresponds mainly to the curved shape of the dental arch to be described. The memory disk 6 is stationary relative to the subject 5. During the shooting rotation about the axis O, the memory disk 6 stores all the information that the beam has to offer the film 2 '. Different layers can be extracted later (without re-imaging) from the total information stored on the memory disk 6.

Utilizing the conventional technique, it is conceivable that the memory disk 6 is a film from which reproducible images are obtained on a principle similar to the above panoramic shooting, except that the subject of the shooting is a memory disk film and visible light, e.g.

Since the memory disk can be added to any panoramic recording device, a separate image reproducing device is an integral part of the invention, with which the layered images can be extracted from the overall image information of the memory disk.

Figure 6 shows an imaging device separate from the imaging device. It kokonaiskuvainformaatiolla provided with a memory disk 6 is set in the holder 7, the motor 10 and the kitkapyö RAN means 11 movable at a given speed in the direction of arrow 14. From the light source 21, a narrow beam of light 22 is directed across the trajectory of the memory plate 6. The memory through the plate 6 is positioned in the print film 8 in the holder 9, so that the motor 12 for moving 73326 6 with the aid of the friction wheel 13 in the direction of the arrow 15. The printing film 8 is narrower in the direction of movement than the memory plate 6, and the printing film 8 is moved at a slower speed than the memory plate 6. Due to the speed difference, only a certain layer of information with the control device 16 and the speed difference is controlled by the control device 17.

In the embodiment of Fig. 7, the memory disk 6 is imaged by a video camera 18 and the image is displayed on the display screen 19. In the normal situation, only the overall information image of the memory disk 6 is seen on the display screen 19, which is vague and does not show any special layer. When the image width of the display screen 19 is adjusted from the controller 20, i.e. the scanning speed of the line is adjusted, the desired layer is displayed on the screen 19. With the image width adjuster 20, the subject can be viewed at different depths layer by layer.

The devices according to Figures 6 and 7 can be calibrated for cooperation so that the same position of the controllers 20 and 17 corresponds to the repetition of the same layer. The devices 6 and 7 can, of course, be built into the same device, in which case the memory disk 6 only needs to be placed once in its holder. Initially, the desired image layer is retrieved on the display screen 19, and then that image layer is stored on the film 8.

It is clear that the current technology offers almost unlimited possibilities in relation to the physical structure of the memory disk and its possibilities of utilization. Computer technology can also be used to store image information.

The above-described application and embodiment are presented only to illustrate the invention and not in a limiting sense of the invention, as the applications and structural implementations of the method according to the invention can vary in many ways within the scope of the following claims.

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Claims (12)

A method for recording and reproducing image information in X-ray panoramic imaging, the method comprising scanning an X-ray beam passing through a subject over the imaging area of the subject and extracting information from the total image format or the layers desired for presentation. A method according to claim 1, characterized in that the memory disk is kept stationary relative to the subject during imaging. Method according to Claim 1 or 2, characterized in that the production of layer-by-layer images from the memory disc is carried out on the principle corresponding to conventional panoramic layer imaging, but the object of the imaging is a memory disc. Method according to Claim 1 or 2, characterized in that the memory disk (6) is inserted into an image reproducing device (Fig. 6 or 7) separate from the imaging device, in which an image corresponding to a certain layer is extracted from the total data of the memory disk (6) on film (8) or display screen (19). between the memory disk (6) pick-up scan and the image print or screen scan. Method according to Claim 3 or 4, characterized in that a film is used as the memory plate, from which images representing different layers are extracted with visible light. Method according to claim 5, characterized in that the layer image printing film (8) is exposed through the memory plate (6) with a narrow beam of light (22) which scans 8 73326 over the memory plate (6) and the printing film (8) while on the printing film (8). 8) and the memory disk (6) is given a sweep speed difference which determines the layer to be extracted from the memory disk (6). Method according to claim 4, characterized in that the memory disk (6) is imaged by a video camera (18) and the line scanning speed of the layer image display screen (19) is adjusted by adjusting the image width to extract the desired layer from the memory disk (6). 7 3 3 2 6 Apparatus for recording image information in X-ray panoramic imaging by a method according to claims 1 and 2, the apparatus comprising an X-ray source (1), image recording means (2) and means (3, 4) for moving the X-ray source (1) relative to the imaging beam (5). characterized in that the image recording means comprise a memory disk (6) immovable relative to the subject (5) for storing the total information of the beam passing through the object, and that the device comprises means for selectively extracting image information corresponding to the desired layer from the memory disk. Device according to Claim 8, characterized in that the shape of the memory plate (6) corresponds substantially to the shape of the object to be described, such as a toothed arc (5). Device according to claim 8, characterized by an image reproducing device (Figures 6 and 7) separate from the imaging device, comprising means (21, 18) for extracting image information from the memory disk (6), a printing film (8) or a display screen (19) and adjusting means (10-17); 20) to cause a speed difference, pick up the memory disk (6) and print the image! between screen sweeps. Device according to claim 10, characterized in that the image reproducing devices comprise means for both the film reproduction (8) and the screen (19), the adjusting means (20) for causing said speed difference in the screen (19) in layers. for image reproduction is provided with a scale or the like, by means of which the control value corresponding to the same layer can be transferred to the control means (10 to 17) which cause said speed difference for the reproduction of the layer image on the film (8). Device according to Claim 8 or 9, comprising a film and cassettes (2) movable relative to the subject, characterized in that a memory disk (6) is arranged between the film (2 ') and the subject (5). 73326